Measurement device, measurement method, and measurement system

ABSTRACT

A measurement device includes a stimulus control unit configured to cause a stimulus generation device to generate an external stimulus complying with a chemotaxis condition of an organism, an imaging unit configured to capture an image of a predetermined imaging range in which the external stimulus is generated, and a measurement unit configured to measure a target organism on the basis of the image captured by the imaging unit.

TECHNICAL FIELD

The present technology relates to a measurement device, a measurementmethod, and a measurement system, and particularly relates to atechnology for measuring a target organism by giving an externalstimulus to an organism exhibiting chemotaxis.

BACKGROUND ART

There has been proposed a measurement device that applies excitationlight having a predetermined wavelength to excite phytoplankton andmeasures the intensity of fluorescence emitted from the excitedphytoplankton to measure the amount of the phytoplankton being present(see Patent Document 1, for example).

CITATION LIST Patent Document Patent Document 1: Japanese PatentApplication Laid-Open No. 2019-165687 SUMMARY OF THE INVENTION Problemsto be Solved by the Invention

The measurement device described above can measure only phytoplanktonexcited by excitation light. Thus, to measure zooplankton or larvae ofaquatic organisms, a method of collecting and testing the zooplankton orthe larvae of aquatic organisms with a water sampler or a plankton netis used. However, such a method is time-consuming and cannot achieveefficient measurement.

Therefore, an object of the present technology is to efficiently measurea target organism.

Solutions to Problems

A measurement device according to the present technology includes astimulus control unit configured to cause a stimulus generation deviceto generate an external stimulus complying with a chemotaxis conditionof an organism, an imaging unit configured to capture an image of apredetermined imaging range in which the external stimulus is generated,and a measurement unit configured to measure a target organism on thebasis of the image captured by the imaging unit.

With the configuration described above, it is possible to performmeasurement on the target organism using the chemotaxis of the organism.

In the measurement device according to the present technology describedabove, it is conceivable that the imaging unit includes a vision sensorconfigured to asynchronously acquire pixel data in accordance with theamount of light incident on each of a plurality of pixelstwo-dimensionally arranged.

This makes it possible to read only pixel data of a pixel in which anevent has occurred and measure the target organism on the basis of thepixel data.

In the measurement device according to the present technology describedabove, it is conceivable that the stimulus control unit causesgeneration of the external stimulus by which the target organismexhibits positive chemotaxis.

This makes it possible to gather the target organism in the imagingrange.

In the measurement device according to the present technology describedabove, it is conceivable that the stimulus control unit causesgeneration of the external stimulus by which a non-target organism otherthan the target organism exhibits negative chemotaxis.

This makes it possible to exclude the non-target organism from theimaging range.

In the measurement device according to the present technology describedabove, it is conceivable that the stimulus control unit causesgeneration of the external stimulus by which a non-target organism otherthan the target organism exhibits negative chemotaxis and the targetorganism does not exhibit negative chemotaxis.

This makes it possible to reduce exclusion of the target organism from atarget range while excluding the non-target organism from the imagingrange.

In the measurement device according to the present technology describedabove, it is conceivable that the stimulus control unit causesgeneration of the external stimulus by which the target organism doesnot exhibit chemotaxis.

This makes it possible to capture an image without being affected by theexternal stimulus.

In the measurement device according to the present technology describedabove, it is conceivable that the external stimulus is light and thestimulus control unit causes application of light by which the targetorganism does not exhibit chemotaxis.

This makes it possible to measure the target organism in a state whereit does not exhibit running performance even in a dark externalenvironment.

In the measurement device according to the present technology describedabove, it is conceivable that the imaging unit captures the image whilebeing moved along a predetermined direction.

This enables wide-range measurement.

In the measurement device according to the present technology describedabove, it is conceivable that the measurement unit derives informationbased on a behavior performed by the target organism in exhibitingchemotaxis on the basis of the image captured by the imaging unit, tospecify the target organism on the basis of the information.

This makes it possible to measure an organism that exhibits chemotaxis.

In the measurement device according to the present technology describedabove, it is conceivable that the measurement unit derives at least oneof the number, the density, or the average activity level of the targetorganism.

This makes it possible to measure the actual status of the targetorganism.

In the measurement device according to the present technology describedabove, it is conceivable that the imaging unit includes the visionsensor and an imaging sensor configured to capture images at regularintervals in accordance with a frame rate.

This makes it possible to measure the target organism using one or bothof the images captured by the vision sensor and the imaging sensor. Inthe measurement device according to the present technology describedabove, it is conceivable that the stimulus control unit causes thestimulus generation device to apply light having a specific wavelengthand intensity, or generate heat.

This makes it possible to measure the target organism using chemotaxisof an organism that exhibits running performance or thermotaxis.

In the measurement device according to the present technology describedabove, it is conceivable that the stimulus control unit causes thestimulus generation device to emit a specific substance.

This makes it possible to measure an organism that exhibits chemotaxisin response to the specific substance.

A measurement method according to the present technology described aboveincludes causing a stimulus generation device to generate an externalstimulus complying with a chemotaxis condition of an organism, capturingan image of a predetermined imaging range to which the external stimulusis output, and measuring a target organism on the basis of the capturedimage.

Also with such a measurement method, effects similar to those producedby the measurement device according to the present technology describedabove can be produced.

A measurement system according to the present technology described aboveincludes a stimulus generation device configured to generate an externalstimulus complying with a chemotaxis condition of an organism, astimulus control unit configured to cause the stimulus generation deviceto generate the external stimulus, an imaging unit configured to capturean image of a predetermined imaging range to which the external stimulusis output, and a measurement unit configured to measure the targetorganism on the basis of the image captured by the imaging unit.

Also with such a measurement system, effects similar to those producedby the measurement device according to the present technology describedabove can be produced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for explaining a configuration of a measurement systemaccording to an embodiment.

FIG. 2 is a view for explaining an example of measurement setting.

FIG. 3 is a view for explaining an example of an operation time chart.

FIG. 4 is a flowchart illustrating a process procedure of a measurementmethod.

FIG. 5 is a view for explaining definition information about a targetorganism.

FIG. 6 is a view for explaining examples of a trajectory and an image ofa detected object.

FIG. 7 is a view for explaining an example of an identification result.

FIG. 8 is a view for explaining a wavelength of applied light in a firstuse example.

FIG. 9 is a view for explaining a wavelength of applied light in asecond use example.

FIG. 10 is a view for explaining a wavelength of applied light in athird use example.

FIG. 11 is a view for explaining measurement in a fourth use example.

FIG. 12 is a view for explaining an example in which the measurementsystem is used in an aquaculture farm.

FIG. 13 is a view for explaining a configuration of a measurement systemaccording to a modification.

FIG. 14 is a view for explaining a configuration of a measurement systemaccording to another modification.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment will be described in the following order.

-   -   <1. Configuration of measurement system>    -   <2. Measurement process>    -   <3. Use examples>    -   [3-1. First use example]    -   [3-2. Second use example]    -   [3-3. Third use example]    -   [3-4. Fourth use example]    -   <4. Specific examples>    -   [4-1. First specific example]    -   [4-2. Second specific example]    -   [4-3. Third specific example]    -   <5. Another example of configuration of measurement system>    -   <6. Conclusion>    -   <7. Present technology>

1. Configuration of Measurement System

First, a configuration of a measurement system 1 as an embodimentaccording to the present technology will be described.

The measurement system 1 is a system that performs measurement on atarget organism being measured using, for example, the chemotaxis of amicroorganism contained in seawater, an organism flying in the air, andthe like. The measurement here is a concept including at least one ofspecification of the type, the number, the activity level, the density,or the characteristic of a target organism, or recording or storage of acaptured image of a target organism. Furthermore, a target organism isnot limited to an organism exhibiting chemotaxis, and includes anorganism not exhibiting chemotaxis.

Here, chemotaxis is an innate behavior performed by an organism inresponse to a directional external stimulus. Examples of an externalstimulus include light, pressure, gravity, a chemical substance(pheromone), electricity, vibration, temperature, contact, and the like.Then, for example, chemotaxis in response to light is referred to asrunning performance, and chemotaxis in response to temperature isreferred to as thermotaxis. Furthermore, movement in a direction towarda source of an external stimulus is referred to as positive chemotaxis,and movement in a direction away from a source of an external stimulusis referred to as negative chemotaxis.

For example, a protozoa flagellate, the genus Euglena, moves toward alight source upon exposure to light. In this example, it can be saidthat a directional external stimulus is light, and the genus Euglenaexhibits positive running performance.

Furthermore, when placed in an environment with a temperature gradient,a nematode moves toward a temperature field (about 25° C.) appropriatefor the nematode. In this example, it can be said that a directionalexternal stimulus is a temperature, and a nematode exhibits thermotaxis.

As described above, it is known that certain organisms exhibitchemotaxis. The measurement system 1 performs measurement on a targetorganism using the chemotaxis of such organisms. Organisms exhibitingchemotaxis are found in both plants and animals. Thus, the measurementsystem 1 can perform measurement concerning a target organismirrespective of whether the target organism is an animal or a plant.

FIG. 1 is a view for explaining a configuration of the measurementsystem 1 according to the embodiment. As illustrated in FIG. 1 , themeasurement system 1 includes a measurement device 2 and a stimulusgeneration device 3.

The measurement device 2 is a device that appropriately controls eachdevice (the measurement device 2 and the stimulus generation device 3)of the measurement system 1 and performs measurement on a targetorganism using the chemotaxis of an organism. The measurement device 2includes a control unit 10, a memory 11, a communication unit 12, agravity sensor 13, an imaging unit 14, and a lens 15.

The control unit 10 includes, for example, a microcomputer including acentral processing unit (CPU), a read only memory (ROM), and a randomaccess memory (RAM), and performs overall control of the measurementsystem 1. In the present embodiment, the control unit 10 functions as astimulus control unit 21, an imaging control unit 22, and a classidentification unit 23. Note that the stimulus control unit 21, theimaging control unit 22, and the class identification unit 23 will bedescribed later in detail.

Furthermore, the control unit 10 performs a process of reading datastored in the memory 11, a process of storing data into the memory 11,and transmission and reception of various data to/from an externaldevice via the communication unit 12.

The memory 11 includes a nonvolatile memory. The communication unit 12performs wired or wireless data communication to/from an externaldevice. The gravity sensor 13 detects a gravitational acceleration(direction of gravity) and outputs a detection result to the controlunit 10. Note that the measurement device 2 is not necessarily requiredto include the gravity sensor 13.

The imaging unit 14 includes a vision sensor 14 a and an imaging sensor14 b. The vision sensor 14 a is a sensor called a dynamic vision sensor(DVS) or an event-based vision sensor (EVS). The vision sensor 14 acaptures an image of a predetermined imaging range through the lens 15.

The vision sensor 14 a is an asynchronous image sensor in which aplurality of pixels having photoelectric conversion elements istwo-dimensionally arranged and a detection circuit that detects anaddress event in real time is provided for every pixel. Note that anaddress event is an event that occurs for every address assigned to eachof the plurality of pixels arranged two-dimensionally, and is, forexample, a phenomenon in which a current value of a current based oncharge generated in the photoelectric conversion element, or the amountof change thereof, exceeds a certain threshold value, or the like.

The vision sensor 14 a detects the presence or absence of occurrence ofan address event for every pixel, and in a case where occurrence of anaddress event is detected, a pixel signal is read as pixel data from thepixel in which the address event has occurred.

The vision sensor 14 a performs a pixel-signal reading operation on apixel in which occurrence of an address event has been detected, andhence can read at a much higher speed than a synchronous image sensorthat performs a reading operation on each of all pixels at apredetermined frame rate. Further, the amount of data read in one frameis small.

Therefore, in the measurement system 1, movement of a target organismcan be detected more quickly by using the vision sensor 14 a.Furthermore, the vision sensor 14 a can reduce the amount of data andalso reduce power consumption.

The imaging sensor 14 b is, for example, a charge coupled device (CCD)image sensor or a complementary metal-oxide-semiconductor (CMOS) imagesensor, in which a plurality of pixels having photoelectric conversionelements is two-dimensionally arranged. The imaging sensor 14 b capturesimages of a predetermined imaging range through the lens 15 at regularintervals in accordance with a frame rate, to generate image data. Notethat, in the measurement device 2, a zone plate, a pinhole plate, or atransparent plate can be used instead of the lens 15.

Note that the vision sensor 14 a and the imaging sensor 14 b arearranged such that the sensors capture images of the substantially sameimaging range through the lens 15. For example, it is only required toplace a half mirror (not illustrated) between the vision sensor 14 a andthe imaging sensor 14 b, and the lens 15 so that a part of lightdispersed by the half mirror is incident on the vision sensor 14 a, andthe other part is incident on the imaging sensor 14 b.

The stimulus generation device 3 is a device that generates (outputs) anexternal stimulus to an imaging range of which image is captured by theimaging unit 14, and gives an external stimulus to an organism presentin the imaging range, and includes a light/heat generation device 30 anda stimulating-substance emission device 31.

The light/heat generation device 30 includes a lighting device 30 a(light source) that applies light to an imaging range and a heat-sourcedevice 30 b (heat source) that applies heat to the imaging range. Thelighting device 30 a is driven on the basis of control of the controlunit 10, and can change the wavelength and intensity of light applied tothe imaging range. The heat-source device 30 b is driven on the basis ofcontrol of the control unit 10, and can change the temperature of theimaging range.

The stimulating-substance emission device 31 includes, for example, acontainer containing pheromone (stimulating substance, chemicalsubstance) and having an opening/closing door, and can emit pheromone toan imaging range by opening and closing the opening/closing door on thebasis of control of the control unit 10. Note that the lighting device30 a and the heat-source device 30 b that are integrally provided as thelight/heat generation device 30 may be provided separately.

Furthermore, light and temperature are common as external stimuli bywhich an organism exhibits chemotaxis, and hence, it is desirable thatthe stimulus generation device 3 includes at least the lighting deviceand the heat-source device 30 b in consideration of general versatility.However, the stimulus generation device 3 may include only thestimulating-substance emission device 31 that emits a stimulatingsubstance as an external stimulus. That is, the stimulus generationdevice 3 is only required to include at least one device that generatesan external stimulus, and may omit any of the lighting device 30 a, theheat-source device 30 b, and the stimulating-substance emission device31.

Furthermore, the stimulus generation device 3 may include a device thatgenerates any of light, a temperature, and a stimulating substance, or acombination of two or more thereof as an external stimulus,specifically, any of the lighting device 30 a, the heat-source device 30b, and the stimulating-substance emission device 31, or a combination oftwo or more thereof.

Furthermore, the stimulus generation device 3 may include a device thatgenerates an external stimulus other than light, a temperature, andpheromone. For example, the stimulus generation device 3 may generate anexternal stimulus complying with a chemotaxis condition under which anorganism exhibits chemotaxis, such as a pressure, a gravity,electricity, vibration, contact, and the like, for example.

2. Measurement Method as Embodiment

Next, an outline of a method for measuring a target organism as theembodiment will be described.

FIG. 2 is a view for explaining an example of measurement setting. FIG.3 is a view for explaining an example of an operation time chart.

The control unit 10 performs measurement in accordance with measurementsetting specified in advance as illustrated in FIG. 2 . In themeasurement setting, a measurement start condition, an operation timechart of the stimulus generation device 3, an identification program(identification method), and a measurement end condition are specified.

As the measurement start condition, a condition for starting measurementis specified, and for example, a time to start measurement, reception ofa measurement start command input via the communication unit 12, or thelike is specified.

As the operation time chart, a time chart according to which thestimulus generation device 3 is caused to generate an external stimuluscomplying with a chemotaxis condition that is a condition of externalstimulus by which an organism exhibits chemotaxis, is specified. Forexample, according to the operation time chart illustrated in FIG. 3A,control is performed such that light is not applied from the lightingdevice 30 a, heat is not output from the heat-source device 30 b, andpheromone is not emitted from the stimulating-substance emission device31 until five minutes elapse from start of measurement. Furthermore, fora duration from five-minute elapse to 10-minute elapse from start of themeasurement, control is performed such that light having a wavelength of420 nm and intensity of 3 W/m² is applied from the lighting device 30 a,heat is not output from the heat-source device 30 b, and pheromone isnot emitted from the stimulating-substance emission device 31.Furthermore, for a duration from 10-minute elapse to 15-minute elapsefrom start of the measurement, control is performed such that light isnot applied from the lighting device 30 a, heat is not output from theheat-source device 30 b, and pheromone is not emitted from thestimulating-substance emission device 31. Furthermore, for a durationfrom 15-minute elapse to 20-minute elapse from start of the measurementto elapse, control is performed such that light having a wavelength of420 nm and intensity of 10 W/m² is applied from the lighting device 30a, heat is not output from the heat-source device 30 b, and pheromone isnot emitted from the stimulating-substance emission device 31.

Furthermore, according to the operation time chart illustrated in FIG.3B, control is performed such that light is not applied from thelighting device 30 a, heat is not output from the heat-source device 30b, and pheromone is not emitted from the stimulating-substance emissiondevice 31 until one minute elapses from start of measurement.Furthermore, for a duration from one-minute elapse to 11-minute elapsefrom start of the measurement, control is performed such that lighthaving a wavelength that is increased from 400 nm by 20 nm every minuteis sequentially applied from the lighting device 30 a at intensity of 5W/m², heat is output from the heat-source device 30 b so that ameasurement range is at 15° C., and pheromone is not emitted from thestimulating-substance emission device 31. Furthermore, for a durationfrom 11-minute elapse to 21-minute elapse from start of the measurement,control is performed such that light having a wavelength that isincreased from 400 nm by 20 nm every minute is sequentially applied fromthe lighting device at intensity of 5 W/m², heat is output from theheat-source device 30 b so that a measurement range is at 20° C., andpheromone is not emitted from the stimulating-substance emission device31. Furthermore, for a duration from 21-minute elapse to 31-minuteelapse from start of the measurement, control is performed such thatlight having a wavelength that is increased from 400 nm by 20 nm everyminute is sequentially applied from the lighting device 30 a atintensity of 5 W/m², heat is output from the heat-source device 30 b sothat a measurement range is at 25° C., and pheromone is not emitted fromthe stimulating-substance emission device 31.

As described above, in the operation time chart, what kind of externalstimulus is to be generated from the stimulus generation device 3 andwhat time such external stimulus is to be generated, for a measurementrange, are specified.

In the identification program, a program (method) for identifying atarget organism is designated, and for example, identification bymachine learning, rule-based identification, identification byinput/output parameters, and the like are specified.

As the measurement end condition, a condition for ending measurement isspecified, and for example, a time to end measurement, reception of ameasurement end command input via the communication unit 12, or the likeis specified.

FIG. 4 is a flowchart illustrating a process procedure of themeasurement method. As illustrated in FIG. 4 , in a step S1, the controlunit 10 determines whether or not the measurement start conditionspecified in the measurement setting is satisfied. Then, the controlunit 10 repeats the step Si until the measurement start condition issatisfied.

On the other hand, in a case where the measurement start condition issatisfied (Yes in the step S1), the stimulus control unit 21 causes thestimulus generation device 3 to operate so as to generate an externalstimulus complying with the chemotaxis condition of an organismaccording to the operation time chart specified in the measurementsetting, in a step S2. In a step S3, the imaging control unit 22controls the imaging unit 14 such that an image of an imaging range iscaptured, to acquire pixel data and image data. Thereafter, in a stepS4, the class identification unit 23 performs an identification process.

In the identification process, the class identification unit 23 performsmeasurement on a target organism on the basis of the image (pixel dataand image data) captured by the imaging unit 14. In the presentembodiment, the class identification unit 23 derives identificationinformation from the image captured by the imaging unit 14 for everycondition for an external stimulus and compares the identificationinformation with definition information stored in the memory 11, todetect the target organism. Furthermore, the class identification unit23 derives an identification result such as the number, the density, andthe average activity level of the detected target organism.

FIG. 5 is a view for explaining the definition information about thetarget organism. FIG. 6 is a view for explaining examples of atrajectory and an image of a detected object. FIG. 7 is a view forexplaining an example of the identification result.

The definition information as illustrated in FIG. 5 is provided forevery target organism and stored in the memory 11. The definitioninformation includes the type (biological name) of the target organism,external stimulus information, chemotactic response information, andimage information. The external stimulus information indicates acondition for an external stimulus by which the target organism exhibitschemotaxis.

The chemotactic response information is information detected mainly onthe basis of an image captured by the vision sensor 14 a, and isinformation based on a behavior performed by the target organism inexhibiting chemotaxis in response to an external stimulus. Thechemotactic response information is, for example, information such as adirection of movement (positive or negative) with respect to a source ofan external stimulus, a speed, and a trajectory. Note that thechemotactic response information may be information detected on thebasis of an image captured by the imaging sensor 14 b. The chemotacticresponse information illustrated in FIG. 5 is merely an example, and apart of the information may be omitted, or other information may beincluded.

The image information is information detected mainly on the basis of animage captured by the imaging sensor 14 b, and is information about anouter shape of the target organism. The image information is, forexample, information such as the size of the target organism and thepresence or absence of a tactile organ. Note that the image informationmay be information detected on the basis of an image captured by thevision sensor 14 a. The image information illustrated in FIG. 5 ismerely an example, and a part of the information may be omitted, orother information may be included.

These pieces of definition information are stored in the memory 11 byrespective different methods for identification programs. For example,in a rule-based identification program, the definition information isset in advance by a user and stored in the memory 11. Furthermore, in anidentification program by machine learning, the definition informationis generated and updated by machine learning in a learning mode andstored in the memory 11.

Furthermore, the definition information may include the direction ofgravity detected by the gravity sensor 13 and external environmentinformation acquired via the communication unit 12. Note that, as theexternal environment information, electric conductivity, a temperature,ph, a concentration of gas (methane, hydrogen, helium, for example), aconcentration of metal (manganese, iron, for example), and the like canbe considered.

The class identification unit 23 detects an object present in an imagingrange on the basis of an image (pixel data) captured by the visionsensor 14 a. For example, the class identification unit 23 creates oneframe data on the basis of pixel data input within a predeterminedperiod, and detects a pixel group within a predetermined range in whichmotion has been detected in the frame data, as an object.

Furthermore, the class identification unit 23 follows an object betweena plurality of pieces of frame data by pattern matching or the like asillustrated in FIGS. 6A and 6C. Then, the class identification unit 23derives a direction of movement with respect to a stimulus source, aspeed, and a trajectory, as identification information, on the basis ofthe result of following the object. In FIGS. 6A and 6C, the position ofan object for every piece of frame data is indicated by a black circle.In the example of FIG. 6A, the object moves in a spiral manner, and inthe example of FIG. 6C, the object moves in a serpentine manner.

Note that a period at which the class identification unit 23 createsframe data from pixel data may be the same as or shorter than a period(frame rate) at which the imaging sensor 14 b acquires image data.

Furthermore, the class identification unit 23 extracts an image portioncorresponding to the object from the image data input from the imagingsensor 14 b for the object from which the identification information hasbeen derived, as illustrated in FIGS. 6B and 6D. Note that FIG. 6Billustrates an image of an object following the trajectory illustratedin FIG. 6A, and FIG. 6D is an image of an object following thetrajectory illustrated in FIG. 6C.

Then, the class identification unit 23 derives the size of the object,the presence or absence of a tactile organ, and the like as theidentification information by image analysis on the basis of theextracted image portion. Note that a known method can be used for theimage analysis, and hence description thereof is omitted here.

The class identification unit 23 collates the external stimulusgenerated by the stimulus generation device 3 and the identificationinformation (the direction of movement, the trajectory, the speed, thesize, the presence or absence of a tactile organ) derived for thedetected object with the definition information conforming to adesignated identification program, to determine whether or not theobject is any target organism. Here, for example, if the derivedidentification information about the object falls within a rangeindicated by the definition information about the target organism, theclass identification unit 23 determines that the derived object is atype indicated by the definition information.

Then, as illustrated in FIG. 7 , the class identification unit 23derives the number of target organisms (for every type) by counting thedetected target organisms of every type. Furthermore, the classidentification unit 23 derives the density and the average activitylevel of target organisms of every type. Note that the density isderived on the basis of the number of target organisms in the imagingrange, and the average activity level is derived on the basis of thespeed of the target organisms. Note that, as illustrated in FIG. 7 , forobjects other than the target organism, the number, the density, and theaverage activity level are derived for every similar characteristic,under the names, “unknown A” and “unknown B”, for example.

Thereafter, in a step S5 (see FIG. 4 ), the class identification unit 23outputs the identification result indicating the type, the number, thedensity, and the average activity level of the detected target organismsand an image captured by the imaging sensor 14 b by storing them intothe memory 11, transmitting them to an external device via thecommunication unit 12, and the like.

In a step S6, the control unit 10 determines whether or not themeasurement end condition specified in the measurement setting issatisfied. Then, the control unit 10 repeats the steps S2 to S5 untilthe measurement end condition is satisfied. In a case where themeasurement end condition is satisfied (Yes in the step S6), the controlunit 10 stops the stimulus generation device 3 and ends the imagecapture in the imaging unit 14, to end the process.

3. Use Examples

Hereinafter, use examples of the measurement system 1 will be described.Note that, in first to fourth use examples described below, light isgenerated from the lighting device 30 a as an external stimulus, and noexternal stimulus (heat, pheromone) is generated from the heat-sourcedevice 30 b and the stimulating-substance emission device 31. Hence,description of control of the heat-source device 30 b and thestimulating-substance emission device 31 is omitted.

3-1. First Use Example

FIG. 8 is a view for explaining a wavelength of applied light in thefirst use example. In the first use example, an external stimulus bywhich a target organism exhibits positive chemotaxis is generated fromthe stimulus generation device 3.

For example, it is assumed that the target organism shows a relationshipbetween running performance and a wavelength as illustrated in FIG. 8 .In such a case, the target organism exhibits positive runningperformance in a wavelength range R1, and thus the measurement settingis specified such that light in the wavelength range R1 by which thetarget organism exhibits positive running performance is applied to animaging range from the lighting device 30 a. Then, the stimulus controlunit 21 causes the lighting device 30 a to apply light in the wavelengthrange R1 by which the target organism exhibits positive runningperformance, to the imaging range, according to the measurement setting.

The imaging control unit 22 causes the vision sensor 14 a to acquirepixel data and causes the imaging sensor 14 b to acquire image datawhile the stimulus generation device 3 is applying light by which thetarget organism exhibits positive running performance.

The class identification unit 23 derives an identification result of thetarget organism on the basis of the pixel data and the image dataacquired by the imaging unit 14.

In the first use example, light by which the target organism exhibitspositive running performance is applied to the imaging range, so thatthe target organism present in the imaging range moves toward the lightsource. Furthermore, in the first use example, the target organismpresent outside the imaging range moves to the light source, and thusmoves to the imaging range. Therefore, in the first use example, thepresence or absence of the target organism can be efficientlydetermined.

3-2. Second Use Example

FIG. 9 is a view for explaining a wavelength of applied light in thesecond use example. In the second use example, unlike in the first useexample, an external stimulus by which an organism other than the targetorganism (, which will be hereinafter referred to as a non-targetorganism) exhibits negative chemotaxis is generated from the stimulusgeneration device 3. Note that, in the second use example, it isdesirable that an external stimulus by which the non-target organismexhibits negative chemotaxis and the target organism does not exhibitnegative chemotaxis is generated from the stimulus generation device 3.However, an external stimulus by which the target organism exhibitsnegative chemotaxis may be generated so long as the external stimuluscauses exhibition of relatively weak negative chemotaxis such as a lowerspeed associated with chemotaxis as compared to that of the non-targetorganism.

For example, it is assumed that the non-target organism shows arelationship between running performance and a wavelength as illustratedin FIG. 9 . In such a case, the non-target organism exhibits negativerunning performance in a wavelength range R10, and thus the measurementsetting is specified such that light in the wavelength range R10 bywhich the non-target organism exhibits negative running performance isapplied to the imaging range from the lighting device 30 a. Then, thestimulus control unit 21 causes the lighting device 30 a to apply lightin the wavelength range R10 by which the non-target organism exhibitsnegative running performance, to the imaging range, according to themeasurement setting.

The imaging control unit 22 causes the vision sensor 14 a to acquirepixel data and causes the imaging sensor 14 b to acquire image datawhile the stimulus generation device 3 is applying light by which thenon-target organism exhibits negative running performance.

The class identification unit 23 derives an identification result of thetarget organism on the basis of the pixel data and the image dataacquired by the imaging unit 14.

In the second use example, light by which the non-target organismexhibits negative running performance is applied to the imaging range,so that the non-target organism present in the imaging range moves in adirection away from the light source, in other words, moves to outsidethe imaging range. Therefore, in the second use example, the non-targetorganism is excluded from the imaging range, and efficient measurementlimited to the target organism can be performed.

3-3. Third Use Example

FIG. 10 is a view for explaining a wavelength of applied light in thethird use example. In the third use example, unlike in the first useexample and the second use example, an external stimulus by which atleast the target organism does not exhibit chemotaxis (positivechemotaxis and negative chemotaxis) is generated from the stimulusgeneration device 3. Note that the external stimulus that does not causeexhibition of chemotaxis includes not only an external stimulus thatdoes not cause exhibition of chemotaxis at all, but also an externalstimulus that causes exhibition of chemotaxis at a lower rate than otherexternal stimuli.

For example, it is assumed that two target organisms show relationshipsbetween a running performance and a wavelength as illustrated in FIG. 10. In such a case, one of the target organisms exhibits runningperformance in response to light in a wavelength range R20, and theother of the target organisms exhibits running performance in responseto light in a wavelength range R21. Thus, the measurement setting isspecified such that light in a wavelength range R22 by which either ofthe target organisms does not exhibit running performance is applied tothe imaging range from the lighting device 30 a. Then, the stimuluscontrol unit 21 causes the lighting device 30 a to apply light in thewavelength range R22 by which either of the target organisms does notexhibit running performance, to the imaging range, according to themeasurement setting.

The imaging control unit 22 causes the vision sensor 14 a to acquirepixel data and causes the imaging sensor 14 b to acquire image datawhile the stimulus generation device 3 is applying light by which eitherof the target organisms does not exhibit running performance.

The class identification unit 23 derives an identification result of thetarget organism on the basis of the pixel data and the image dataacquired by the imaging unit 14.

Here, in the case of measuring a target organism in a place wherenatural light does not reach, such as at night or in deep water, it isnecessary to apply illumination light to the imaging range. At thattime, if illumination light by which the target organism exhibitschemotaxis is applied to the imaging range, the target organism in theimaging range cannot be accurately measured. Specifically, to applyillumination light by which the target organism exhibits positiverunning performance to the imaging range would increase the number oftarget organisms in the imaging range. Furthermore, to applyillumination light by which the target organism exhibits negativerunning performance to the imaging range would reduce the number oftarget organisms in the imaging range.

Then, in the third use example, illumination light by which the targetorganism does not exhibit chemotaxis is applied to the imaging range,and thus it is possible to capture an image without affecting the targetorganism, which enables efficient measurement in an original naturalenvironment.

3-4. Fourth Use Example

FIG. 11 is a view for explaining measurement in a fourth use example. Inthe fourth use example, the measurement device 2 captures an image whilemoving in the third use example. Thus, the lighting device 30 a applieslight in the wavelength range R22 by which either of the targetorganisms does not exhibit running performance, to the imaging range, inthe manner similar to that in the third use example.

Then, as illustrated in FIG. 11 , the measurement device 2 moves alongthe optical axis direction of the light applied from the light/heatgeneration device 30 of the stimulus generation device 3, for example.Note that the measurement device 2 may be connected to a movingmechanism (not illustrated) and controlled such that it moves under thecontrol of the control unit 10, or may be moved manually. Furthermore,the measurement device 2 is only required to be capable of moving alonga predetermined direction. For example, the measurement device 2 maymove along the direction of gravity or may move along a directionorthogonal to the optical axis of light applied from the light/heatgeneration device 30.

Then, the imaging control unit 22 causes the vision sensor 14 a toacquire pixel data and causes the imaging sensor 14 b to acquire imagedata while the measurement device 2 is moving along the optical axisdirection.

The class identification unit 23 derives an identification result of thetarget organism on the basis of the pixel data and the image dataacquired by the imaging unit 14.

In the fourth use example, the imaging range is moved, which enablesmeasurement of target organisms in a wide range. Furthermore, in thefourth use example, for example, in a case where the optical axisdirection and the direction of gravity coincide with each other and themeasurement device 2 is moved in the direction of gravity, adistribution of target organisms in the direction of gravity can bemeasured.

4. Specific Examples

The measurement system 1 is intended to be used underwater and on land.For example, in water, the measurement system 1 is intended to be usedfor measurement performed on organisms used for feed (rotifer, brineshrimp, copepod), parasites parasitic on cultivated animals (fish louse,parasitic copepod, parasitic ciliate, Benedenia seriolae), larvae ofdeep-sea animals, zooplankton indigenous to hydrothermal plume,phytoplankton causing red tide, and fish, as target organisms.Furthermore, on land, the measurement system 1 is intended to be usedfor measurement performed on harmful insects such as a mosquito, a moth,or a fly, as target organisms. Below, description will be given by wayof specific examples.

4-1. First Specific Example

FIG. 12 is a view for explaining an example in which the measurementsystem 1 is used in an aquaculture farm. In a first specific example, asillustrated in FIG. 12 , the measurement system 1 is placed in anaquaculture farm, and estimates the amount of larvae of brine shrimpsused for feed in fish culture. Furthermore, in the first specificexample, it is assumed that machine learning is designated as theidentification program.

In this case, the class identification unit 23 estimates the number ofbrine shrimps (the amount of larvae) by machine learning in anenvironment in the aquaculture farm where suspended matters such aszooplankton and dust coexist.

Here, a brine shrimp is known as exhibiting remarkable runningperformance in response to light having a wavelength of around 420 nm.Furthermore, copepods that account for most, 80% or more on average, ofzooplankton community are known as exhibiting remarkable runningperformance in response to light having a wavelength of around 400 to500 nm.

Thus, in a learning mode, the stimulus control unit 21 causes thelighting device 30 a to apply light having a wavelength of 420 nm andlight having a wavelength of 530 nm to each of liquid samples, eachcontaining only one of brine shrimps, copepods, and dust. The imagingcontrol unit 22 causes the imaging unit 14 to operate and capture animage while the stimulus generation device 3 is applying light of eachwavelength.

The class identification unit 23 learns identification information aboutthe brine shrimps, the copepods, and the dust as training data on thebasis of the image captured by the imaging unit 14.

Thus, in the learning mode, definition information about the brineshrimps, the copepods, and the dust is generated on the basis of therespective pieces of identification information about the brine shrimps,the copepods, and the dust in a case where light having a wavelength of420 nm is applied, and respective pieces of the identificationinformation about the brine shrimps, the copepods, and the dust in acase where light having a wavelength of 530 nm is applied.

Then, in the aquaculture farm where the brine shrimps, the zooplankton,and the dust coexist, the stimulus control unit 21 causes the lightingdevice 30 a to apply light having a wavelength of 420 nm and lighthaving a wavelength of 530 nm. The imaging control unit 22 causes theimaging unit 14 to operate and capture an image while the stimulusgeneration device 3 is applying light of each wavelength.

The class identification unit 23 derives the amount of larvae of thebrine shrimps (identification result) using the definition informationlearned in the learning mode on the basis of the image captured by theimaging unit 14.

As described above, the measurement system 1 can efficiently andaccurately derive the identification result of the target organism inthe unknown liquid sample by learning the characteristic of the targetorganism in advance by machine learning.

4-2. Second Specific Example

In a second specific example, the number of larval fish that mostlyinhabit shallow sea areas is estimated. Furthermore, in the secondspecific example, it is assumed that rule base is designated as theidentification program.

Here, it is assumed that larval fish to be measured has green visualsensitivity characteristic and has blue visual sensitivitycharacteristic when becoming an adult fish. That is, the larval fish tobe measured exhibits running performance in response to light having awavelength of around 550 nm (green light).

In this case, the stimulus control unit 21 causes the lighting device 30a to apply light having a wavelength of 550 nm. The imaging control unit22 causes the imaging unit 14 to operate and capture an image while thestimulus generation device 3 is applying light. The class identificationunit 23 derives an identification result of the larval fish using thedefinition information stored in the memory 11 in accordance with therule base on the basis of the image captured by the imaging unit 14.

4-3. Third Specific Example

In a third specific example, the number of nematodes existing in soil isestimated. Furthermore, in the third specific example, it is assumedthat rule base is designated as the identification program.

Here, a nematode to be measured is known as exhibiting thermotaxis inwhich it moves to a temperature field at around 25° C.

The stimulus control unit 21 causes the heat-source device 30 b tooperate so that a measurement range is at 25° C. The imaging controlunit 22 causes the imaging unit 14 to operate and capture an image whilethe temperature is under the control of the heat-source device 30 b.

The class identification unit 23 derives an identification result of thenematodes using the definition information stored in the memory 11 inaccordance with the rule base on the basis of the image captured by theimaging unit 14.

5. Another Example of Configuration of Measurement System

Note that the embodiment is not limited to the specific examplesdescribed above, and can adopt various configurations as modifications.

In the embodiment described above, the measurement system 1 includes onemeasurement device 2 and one stimulus generation device 3. However, thenumber of the measurement devices 2 or the stimulus generation devices 3is not limited to one, and a plurality of measurement devices 2 or aplurality of stimulus generation devices 3 may be provided.

FIG. 13 is a view for explaining a configuration of a measurement system100 according to a modification. As illustrated in FIG. 13 , themeasurement system 100 of the modification includes one measurementdevice 2 and two stimulus generation devices 3 (light/heat generationdevices 30). The two light/heat generation devices 30 are arranged so asto be capable of applying light in directions orthogonal to each other,and can apply light having wavelengths different from each other to theimaging range.

In the measurement system 100 described above, light of differentwavelengths can be applied from the two light/heat generation devices30, and thus identification information about a target organismexhibiting running performance in response to light of differentwavelengths can be derived by one-time measurement, which enablesefficient measurement.

FIG. 14 is a view for explaining a configuration of a measurement system200 according to another modification. As illustrated in FIG. 14 , themeasurement system 200 of the modification includes two measurementdevices 2 and one stimulus generation device 3 (light/heat generationdevice 30). The two measurement devices 2 are arranged so as to becapable of capturing images in directions orthogonal to each other.

In the measurement system 100 described above, images can be captured bythe two measurement devices 2 (imaging units 14), and thusthree-dimensional movement of an object can be detected, which enablesmore efficient measurement.

Note that, in a case where two measurement devices 2 are provided, oneof the measurement devices 2 may include only the imaging unit 14.

Furthermore, in the embodiment described above, the imaging unit 14includes the vision sensor 14 a and the imaging sensor 14 b. However,the imaging unit 14 may include either the vision sensor 14 a or theimaging sensor 14 b so long as an image from which identificationinformation indicating at least chemotaxis can be derived can becaptured. Furthermore, the imaging unit 14 may include a single photonavalanche diode (SPAD) sensor instead of the vision sensor 14 a and theimaging sensor 14 b.

Furthermore, in the embodiment described above, identificationinformation is derived on the basis of pixel data acquired by the visionsensor 14 a and image data acquired by the imaging sensor 14 b. However,identification information may be derived on the basis of one or both ofpixel data acquired by the vision sensor 14 a and image data acquired bythe imaging sensor 14 b. Furthermore, control may be performed such thatonly the vision sensor 14 a is driven with the imaging sensor 14 b keptstopped, and the vision sensor 14 a and the imaging sensor 14 b aredriven when the vision sensor 14 a acquires pixel data.

Furthermore, in the embodiment described above, the lighting device 30 acan change the wavelength and intensity of applied light. However, thelighting device may be configured so as to be capable of selecting thepresence or absence of blinking, changing the frequency of blinking,selecting the presence or absence of polarized light, changing thedirection of polarized light, changing the size of the light source,changing the shape of the light source, changing the orientation of thelight source with respect to the direction of gravity and the directionof the measurement device 2, the direction of propagation, or the like,in addition to, or instead of, changing the wavelength and intensity ofapplied light, in accordance with the chemotaxis of an organism.

6. Conclusion of Embodiment

As described above, the measurement device 2 of the embodiment includesthe stimulus control unit 21 configured to cause the stimulus generationdevice 3 to generate an external stimulus complying with a chemotaxiscondition of an organism, the imaging unit 14 configured to capture animage of a predetermined imaging range in which the external stimulus isgenerated, and a measurement unit (class identification unit 23)configured to measure a target organism on the basis of the imagecaptured by the imaging unit 14.

With the configuration described above, it is possible to performmeasurement on the target organism using the chemotaxis of the organism.

Therefore, the measurement device 2 can efficiently measureplants/animals as target organisms using the chemotaxis of the organism.

In the measurement device 2 according to the present technologydescribed above, the imaging unit 14 includes the vision sensor 14 aconfigured to asynchronously acquire pixel data in accordance with theamount of light incident on each of a plurality of pixelstwo-dimensionally arranged.

This makes it possible to read only pixel data of a pixel in which anevent has occurred and measure the target organism on the basis of thepixel data.

Therefore, the measurement device 2 can reduce power consumption.

In the measurement device 2 according to the present technologydescribed above, the stimulus control unit 21 generates an externalstimulus by which the target organism exhibits positive chemotaxis.

This makes it possible to gather the target organism in the imagingrange.

Therefore, the measurement device 2 can efficiently measure the presenceor absence of the target organism.

In the measurement device 2 according to the present technologydescribed above, the stimulus control unit 21 causes generation of anexternal stimulus by which a non-target organism other than the targetorganism exhibits negative chemotaxis.

This makes it possible to exclude the non-target organism from theimaging range.

Therefore, the measurement device 2 can exclude the non-target organismand perform measurement limited to the target organism.

In the measurement device 2 according to the present technologydescribed above, the stimulus control unit 21 causes generation of anexternal stimulus by which a non-target organism other than the targetorganism exhibits negative chemotaxis and the target organism does notexhibit negative chemotaxis.

This makes it possible to reduce exclusion of the target organism from atarget range while excluding the non-target organism from the imagingrange.

Therefore, the measurement device 2 can accurately measure the targetorganism.

In the measurement device 2 according to the present technologydescribed above, the stimulus control unit 21 causes generation of anexternal stimulus by which the target organism does not exhibitchemotaxis.

This makes it possible to capture an image without being affected by theexternal stimulus. Therefore, the measurement device 2 can accuratelymeasure the target organism without being affected by the externalstimulus.

In the measurement device 2 according to the present technologydescribed above, the external stimulus is light and the stimulus controlunit 21 causes application of light by which the target organism doesnot exhibit chemotaxis.

This makes it possible to measure the target organism in a state whereit does not exhibit running performance even in a dark externalenvironment.

Therefore, the measurement device 2 can accurately measure the targetorganism without being affected by the external stimulus.

In the measurement device 2 according to the present technologydescribed above, the imaging unit 14 captures an image while being movedalong a predetermined direction.

This enables wide-range measurement.

Therefore, the measurement device 2 can measure the target organism in awider range.

In the measurement device 2 according to the present technologydescribed above, the measurement unit (class identification unit 23)derives information (identification information) based on a behaviorperformed by the target organism in exhibiting chemotaxis on the basisof the image captured by the imaging unit 14, to specify the targetorganism on the basis of the information.

This makes it possible to measure an organism that exhibits chemotaxis.

Therefore, the measurement device 2 can more accurately specify thetarget organism using the information based on a behavior performed inexhibiting chemotaxis.

In the measurement device 2 according to the present technologydescribed above, the measurement unit (class identification unit 23)derives at least one of the number, the density, or the average activitylevel of target organism.

This makes it possible to measure the actual status of the targetorganism.

Therefore, the measurement device 2 can specify at least one of thenumber, the density, or the average activity level of target organism.

In the measurement device 2 according to the present technologydescribed above, the imaging unit 14 includes the vision sensor 14 a andthe imaging sensor 14 b that captures images at regular intervals inaccordance with a frame rate.

This makes it possible to measure the target organism using one or bothof the images captured by the vision sensor 14 a and the imaging sensor14 b.

Furthermore, the measurement device 2 uses information based on theimage captured by the vision sensor 14 a, and thus the image captured bythe imaging sensor 14 b may be coarse as compared with that in a casewhere the target organism is measured using only the imaging sensor.This makes it possible to capture an image in a wider range than that ina case where only the imaging sensor is used, with the same number ofpixels.

In the measurement device 2 according to the present technologydescribed above, the stimulus control unit 21 causes the stimulusgeneration device 3 to apply light having a specific wavelength andintensity, or generate heat.

This makes it possible to measure the target organism using chemotaxisof an organism that exhibits running performance or thermotaxis.

Therefore, the measurement device 2 can efficiently measure the targetorganism using the chemotaxis of an organism that exhibits runningperformance or thermotaxis.

In the measurement device 2 according to the present technologydescribed above, the stimulus control unit 21 causes the stimulusgeneration device 3 to emit a specific substance.

This makes it possible to measure an organism that exhibits chemotaxisin response to the specific substance.

Therefore, the measurement device 2 can efficiently measure the targetorganism using the chemotaxis of an organism that exhibits chemotaxis inresponse to the specific substance.

The measurement system 1 according to the present technology describedabove includes the stimulus generation device 3 configured to output anexternal stimulus complying with a chemotaxis condition of an organism,the stimulus control unit 21 configured to cause the stimulus generationdevice 3 to generate the external stimulus, the imaging unit 14configured to capture an image of a predetermined imaging range to whichthe external stimulus is output, and the measurement unit (classidentification unit 23) configured to measure a target organism on thebasis of the image captured by the imaging unit 14.

Also with such a measurement system 1, functions and effects similar tothose provided by the measurement device 2 according to the presenttechnology described above can be provided.

Note that the effects described in the present specification are merelyexamples and are not limitative, and other effects may be provided.

7. Present Technology

The present technology can also adopt the following configurations.

(1)

A measurement device including

a stimulus control unit configured to cause a stimulus generation deviceto generate an external stimulus complying with a chemotaxis conditionof an organism,

an imaging unit configured to capture an image of a predeterminedimaging range in which the external stimulus is generated, and

a measurement unit configured to measure a target organism on the basisof the image captured by the imaging unit.

(2)

The measurement device according to (1),

in which the imaging unit

includes a vision sensor configured to asynchronously acquire pixel datain accordance with the amount of light incident on each of a pluralityof pixels two-dimensionally arranged.

(3)

The measurement device according to (1) or (2),

in which the stimulus control unit

causes generation of the external stimulus by which the target organismexhibits positive chemotaxis.

(4)

The measurement device according to any of (1) to (3),

in which the stimulus control unit

causes generation of the external stimulus by which a non-targetorganism other than the target organism exhibits negative chemotaxis.

(5)

The measurement device according to (4),

in which the stimulus control unit

causes generation of the external stimulus by which a non-targetorganism other than the target organism exhibits negative chemotaxis andthe target organism does not exhibit negative chemotaxis.

(6)

The measurement device according to (1) or (2),

in which the stimulus control unit causes generation of the externalstimulus by which the target organism dose not exhibit chemotaxis.

(7)

The measurement device according to (6),

in which the external stimulus is light, and

the stimulus control unit causes application of light by which thetarget organism does not exhibit chemotaxis.

(8)

The measurement device according to any of (1) to (7),

in which the imaging unit

captures an image while being moved along a predetermined direction.

(9)

The measurement device according to any of (1) to (8)

in which the measurement unit

derives information based on a behavior performed by the target organismin exhibiting chemotaxis on the basis of the image captured by theimaging unit, and specifies the target organism on the basis of theinformation.

(10)

The measurement device according to (9),

in which the measurement unit

derives at least one of the number, the density, or the average activitylevel of the target organism.

(11)

The measurement device according to (2),

in which the imaging unit

includes the vision sensor and an imaging sensor configured to captureimages at regular intervals in accordance with a frame rate.

(12)

The measurement device according to any of (1) to (11),

in which the stimulus control unit

causes the stimulus generation device to apply light having a specificwavelength and intensity, or generate heat.

(13)

The measurement device according to any of (1) to (12),

in which the stimulus control unit

causes the stimulus generation device to emit a specific substance.

(14)

A measurement method including

causing a stimulus generation device to generate an external stimuluscomplying with a chemotaxis condition of an organism,

capturing an image of a predetermined imaging range to which theexternal stimulus is output, and

measuring a target organism on the basis of the captured image.

(15)

A measurement system including

a stimulus generation device configured to generate an external stimuluscomplying with a chemotaxis condition of an organism,

a stimulus control unit configured to cause the stimulus generationdevice to generate the external stimulus,

an imaging unit configured to capture an image of a predeterminedimaging range to which the external stimulus is output, and

a measurement unit configured to measure the target organism on thebasis of the image captured by the imaging unit.

REFERENCE SIGNS LIST

-   -   1 Measurement system    -   2 Measurement device    -   3 Stimulus generation device    -   10 Control unit    -   14 Imaging unit    -   14 a Vision sensor    -   14 b Imaging sensor    -   21 Stimulus control unit    -   22 Imaging control unit    -   23 Class identification unit

1. A measurement device comprising: a stimulus control unit configuredto cause a stimulus generation device to generate an external stimuluscomplying with a chemotaxis condition of an organism; an imaging unitconfigured to capture an image of a predetermined imaging range in whichthe external stimulus is generated; and a measurement unit configured tomeasure a target organism on a basis of the image captured by theimaging unit.
 2. The measurement device according to claim 1, whereinthe imaging unit includes a vision sensor configured to asynchronouslyacquire pixel data in accordance with an amount of light incident oneach of a plurality of pixels two-dimensionally arranged.
 3. Themeasurement device according to claim 1, wherein the stimulus controlunit causes generation of the external stimulus by which the targetorganism exhibits positive chemotaxis.
 4. The measurement deviceaccording to claim 1, wherein the stimulus control unit causesgeneration of the external stimulus by which a non-target organism otherthan the target organism exhibits negative chemotaxis.
 5. Themeasurement device according to claim 4, wherein the stimulus controlunit causes generation of the external stimulus by which a non-targetorganism other than the target organism exhibits negative chemotaxis andthe target organism does not exhibit negative chemotaxis.
 6. Themeasurement device according to claim 1, wherein the stimulus controlunit causes generation of the external stimulus by which the targetorganism does not exhibit chemotaxis.
 7. The measurement deviceaccording to claim 6, wherein the external stimulus is light, and thestimulus control unit causes application of light by which the targetorganism does not exhibit chemotaxis.
 8. The measurement deviceaccording to claim 1, wherein the imaging unit captures the image whilebeing moved along a predetermined direction.
 9. The measurement deviceaccording to claim 1, wherein the measurement unit derives informationbased on a behavior performed by the target organism in exhibitingchemotaxis on a basis of the image captured by the imaging unit, andspecifies the target organism on a basis of the information.
 10. Themeasurement device according to claim 9, wherein the measurement unitderives at least one of the number, density, or average activity levelof the target organism.
 11. The measurement device according to claim 2,wherein the imaging unit includes the vision sensor and an imagingsensor configured to capture images at regular intervals in accordancewith a frame rate.
 12. The measurement device according to claim 1,wherein the stimulus control unit causes the stimulus generation deviceto apply light having a specific wavelength and intensity, or generateheat.
 13. The measurement device according to claim 1, wherein thestimulus control unit causes the stimulus generation device to emit aspecific substance.
 14. A measurement method comprising: causing astimulus generation device to generate an external stimulus complyingwith a chemotaxis condition of an organism; capturing an image of apredetermined imaging range to which the external stimulus is output;and measuring a target organism on a basis of the captured image.
 15. Ameasurement system comprising: a stimulus generation device configuredto generate an external stimulus complying with a chemotaxis conditionof an organism; a stimulus control unit configured to cause the stimulusgeneration device to generate the external stimulus; an imaging unitconfigured to capture an image of a predetermined imaging range to whichthe external stimulus is output; and a measurement unit configured tomeasure the target organism on a basis of the image captured by theimaging unit.